With developing of the Internet, various network services and advanced multimedia systems have been proposed. Since a real-time service is sensitive to some functions such as network transmission delay and delay jitter, when there are services like File Transfer Protocol (FTP) with high burst quality or Hyper Text Transfer Protocol (HTTP) with image files etc., real-time services will be greatly affected. In addition, since multimedia services occupy a wide range of bandwidths, the critical services to be guaranteed cannot be transmitted reliably in the prior networks. Therefore, in order to guarantee reliable transmission for the critical services, various Quality of Service (QoS) techniques have been proposed. Internet Engineering Task Force (IETF) has put forward many service models and mechanisms for QoS requirements. At present, a fairly recognized technique in the art is to adopt Integrated Service (Int-Serv) model in access area or edge area of a network, while to adopt Differentiated Service (Diff-Serv) model in core area of the network.
The Diff-Serv model guarantees QoS only by setting priorities, which makes actual effect unpredictable though the line utilization ratio is high. Therefore, an independent bearer control layer is introduced for the Dif-Serv model of a backbone network, a dedicated Diff-Serve QoS signaling mechanism is established and a dedicated resource management layer for managing topology resources of the network is established for Diff-Serv network. Such resource managing Diff-Service mode is called Diff-Service model with independent bearer control layer. FIG. 1 illustrates such a model of a Diff-Service model with independent bearer control layer. As shown in FIG. 1, a bearer control layer 102 is located between a bearer network 103 and a service control layer 101 in this model. A Call Agent (CA) in service control layer 101 is a service server, such as a soft switch which can implement soft switch function. Bearer control layer 102 includes one or more than one bearer network resource manager, which is in charge of configuring management rules and network topology, assigning resource allocation for a client's service bandwidth request, controlling and managing all bearer network resource managers to transfer the client's service bandwidth application request and result as well as the route path information allocated for service application in between by way of signaling, for example, controlling and managing communications among bearer network resource managers 1, 2 and 3. In bearer network 103, each bearer network resource manager manages a given bearer network area which is called management domain of corresponding bearer network resource manager, for example, bearer network resource manager 1 manages management domain 105, bearer network resource manager 2 manages management domain 106 and bearer network resource manager 3 manages management domain 107. Bearer network 103 includes an Edge Router (ER), a Border Router (BR) and a core router 104, the ER, BR and core router all belonging to the bearer network and generally called Connection Nodes (CNs).
The bearer control layer will determine a path for a user service when processing the user's service bandwidth application, and the bearer network resource manager will notify ER to forward service stream according to the specified path. Routes in a bearer network resource manager include two types: signaling route and service route. The signaling route means a procedure of how each bearer network resource manager finds the next hop of bearer network resource manager. The service route means a procedure of how a bearer network resource manager finds a proper bearer Label Switching Path (LSP) according to service stream information. A service route comprises an intra-domain route and an inter-domain route.
Generally speaking, the bearer network forwards user service streams with a specified route according to the path determined by the bearer control layer. At present, an LSP is established along the service stream path specified by the bearer control layer by way of resource reservation manner, by utilizing Multi-Protocol Label Switching (MPLS) technique, or an end to end LSP is established by utilizing explicit route mechanism based on Resource ReSerVation Setup Protocol with Traffic Engineering extensions (RSVP-TE) or Constraint Route Label Distribution Protocol (CR-LDP).
At present, there are several schemes for route path establishment and resource allocation of a bearer network resource manager as follows:
One scheme is a technique of establishing route path on requirement, namely when a calling party initiates a call, a bearer network resource manager acquires LSP information real-timely from a router of a bearer network according to the current network topology and management rule, selects an LSP suitable for the current call from the LSP information, and releases this LSP after the current call is finished. In this scheme, because a bearer network resource manager acquires LSP information directly from a bearer network and it is required to reacquire and reselect corresponding LSP for each call, LSP information cannot be repeatedly used, which results in high routing load and low efficiency of a bearer network resource manager.
Another scheme utilizes bandwidth broker model of a Quality-of-Service backbone (QBone) experimental network. Its network structure model is shown in FIG. 2. In this model, a corresponding bandwidth broker is set for each Diff-Serv management domain, such as bandwidth brokers 1, 2 and 3. The bandwidth broker is in charge of processing bandwidth application requests from user hosts, service servers or network maintainers, and determining whether to authorize user's bandwidth application according to the resource reservation state of the current network, the configured strategy as well as the Service Level Agreement (SLA) signed with the user. This bandwidth broker records various kinds of static or dynamic information, such as SLA configuration information, topology information of physical network, configuration information and strategy information of the router, user authentication information, current resource reservation information, network occupation state information, and also records route information so as to confirm user's service stream path and location of cross-domain downstream bandwidth broker.
The internal structure of the bandwidth broker in FIG. 2 is shown in FIG. 3, including: an inter-domain interface, which communicates with bandwidth brokers of other bearer control layers; a user service interface, which communicates with a service server, a host/user and a network maintenance device; a strategy interface used for strategy control; a network management interface; a route information storage, which records intra-domain route information in a bearer network resource manager; a database; an intra-domain interface and a simple strategy service module. The modules inside the bandwidth broker cooperate with each other. This bandwidth broker records various kinds of static or dynamic information, such as SLA configuration information, topology information of physical network, configuration information and strategy information of the router, user authentication information, current resource reservation information, network occupation state information, and also records route information so as to confirm user's service stream path and location of cross-domain downstream bandwidth broker.
In the network structure model shown in FIG. 2, a router in a bearer network reports route path resource information to a bandwidth broker real-timely. The bandwidth broker acquires route path information suitable for calling service of the client from the reported route path resource information, selects a route path for the call service of the client and reserves bandwidth resource in the route path. This technique scheme has disadvantages as follows, topology and management is very complicated because a bandwidth broker directly manages resources and configuration information of all routers in the area; a route table needs to be updated frequently because a bandwidth broker needs to record dynamic route information of the local area, which will lead to instable network reservation; the service route determined by a bandwidth broker according to dynamic route information of the local area is difficult to be identical with the actual forwarding route of the service stream.
An alternative scheme is Rich QoS scheme presented by NEC company. Its network structure model is shown in FIG. 4, including a QoS server 401 as the key component, a strategy server 402, a catalogue server 403 and a network management monitoring server 404 which are auxiliary with the QoS server. Here, the QoS server is in charge of allocating desirable bearer path for QoS service requests according to topology and resource condition of bearer network. The strategy server 402 sets parameters and configuration of relevant routers according to QoS server 401 and strategy configuration information such as management interface. The catalogue server 403 is a unified and intensive database used for storing network device configuration information, user information and QoS information. The network management monitoring server 404 is in charge of collecting information, such as congestion state of routers and links in the bearer network, for reference for the QoS server when selecting a route for a service application.
In this scheme, LSP information is configured in the QoS server. The QoS server acquires LSP information suitable for the client's calling service from the LSP information, and selects an LSP for the client's calling service and reserves bandwidth resources in the LSP. After a service server sends a bandwidth request to the QoS server, the QoS server records connection resource request for this call, allocates a satisfying bearer path for the service request according to QoS requirements as well as the current topology and the current resource condition of the bearer network, and then returns allocation result to the service server. The LSP information configured in the QoS server is divided into various levels based on priority, and the QoS server selects high-priority LSP information for service requests with high priority and low-priority LSP information for service requests with low priority. However, if there are large amount of service requests with low priorities and small amount of service requests with high priorities, it will lead to network congestion upon services with low priorities and bandwidth idle upon services with high priorities, therefore this scheme is inflexible and low-effective in routing.
In addition, this Rich QoS scheme relates to a pretty complex bearer network with a large number of routers. Meanwhile, QoS server and strategy server notify edge routers by using explicit route MPLS LSP establishment technique and a mode of establishing end-to-end LSP, resulting in poor expansibility and limited network scale. Thus, this scheme is not applicable for end-to-end service requirements in a public network.
The above are several schemes for establishing and allocating resources. As for how to include service route path and signaling route path in multiple route paths and how to select a suitable route, multiple algorithms can be adopted. The selection of service route path and signaling route path can adopt the same or different algorithms. However, since each domain is singly managed by a certain bearer network resource manager, a bearer network resource manager cannot know LSP resource conditions in other domains managed by other bearer network resource managers, which will bring uncertain factors for route availability and thus affect service efficiency of network.
For instance, when a forward routing manner is adopted between a source bearer network resource manager and a destination bearer network resource manager, with reference to network structure shown in FIG. 5, intra-domain routes and inter-domain routes are sequentially selected from a source ER to a destination ER hop by hop, but this route selection manner is liable to lead to route selection failure. This is because if a service stream is to be transmitted from ER2 to ER3, all the four inter-domain LSPs, i.e. LSP11, LSP12, LSP13 and LSP14, between bearer network resource managers 1 and 2 are all selectable; however, when LSP resources between BR3 and ER3 inside bearer network resource manager 2 are used up while resources between BR4 and ER3 are in idle state, bearer network resource manager 1 will still select an inter-domain LSP according to route load sharing algorithm since it does not know LSP resource occupation condition inside the domain managed by bearer network resource manager 2. If LSP11 or LSP13 is selected, the route selection from bearer network resource manager 1 to bearer network resource manager 2 will be failed, thus leading to failure of entire routing. Therefore, in the above case, only adopting forward route selection manner cannot obtain reasonable resource allocation, and the main reason is that one bearer network resource manager does not know LSP resource utilization condition in those domains managed by other bearer network resource managers. In addition, there may be some rule constraints for certain specified performance requirements and services in domains managed by certain bearer network resource managers, for example some specified streams are allowed to or forbidden to pass in a certain intra-domain LSP, which may also lead to route selection failure. However, if simply replacing forward route selection with backward route selection, the above-mentioned problem is also inevitable. Thus requirements of various services cannot be satisfied well.
For another instance, in the prior art, the path through which a service request will pass and occupied bandwidth in this path are calculated according to routing tables in each router. In this case, while implementing intra-domain route selection, once information of a certain router is updated, for example when developing a new service or a service is updated, information of the bearer network resource manager on bearer control layer should also be updated, which may lead to instability of network reservation. Meanwhile, bearer network resource manager needs to record dynamic route information in the local domain, which may result in a problem that routing table will be updated frequently. In this case, network reservation will be instable, and it is also difficult to guarantee the determined service route to be the same as the actual forwarding route of the service stream.